Insulation system



L A T E N A M R O F D c INSULATION SYSTEM Filed May a, 1966 5SheetsSheet l N A M W F D S E L R A H JOHN REEVES ATTORNEY y 1968 c. D.FORMAN ETAL 3,381,843

INSULATION SYSTEM Filed May 6, 1966 5 Sheets-Sheet 2 r (\WWW co K R. Q QQ 0 I INVENTORS CHARLES 0. FORMAN w BY JOHN REEVES LL mwommawr y 1968 c.D. FORMAN ETAL 3,381,843

INSULATION SYSTEM Filed May 6, 1966 5 Sheets$heet 5 .INVENTORS CHARLESD. FORMAN BY JOHN F. REEVES Ema/FM ATTORNEY United States Patent3,381,843 INSULATION SYSTEM Charles D. Forman, Elizabeth, NJ., and JohnF. Reeves,

Milwaukee, Wis., assignors to Esso Research and Engineering Company, acorporation of Delaware Filed May 6, 1966, Ser. No. 548,309 4 Claims.(Cl. 2209) The present invention relates to insulated cargo tanks of thetype adapted to store liquefied natural gas and the like at cryogenictemperatures and, more particularly, to a new and improved system ofinterlocking wall panels and plug panels of thermal insulation whichform an impervious and stable cargo barrier.

The insulating wall panels of the invention are generally fiat for flatwall portions, are generally L-shaped for corner portions defined by theintersections of two walls, and are generally boxlike for cornerportions defined by the intersections of three walls. All of the wallpanels have ascendingly stepped lateral edges. The plug panels areinterposed in mating relation between the ascendingly stepped edges ofthe aforementioned wall panels and are correspondingly either ofgenerally fiat or L-shaped configurations and have descendingly steppedside edges. As an important aspect of the invention, the L-shaped andboxlike corner panels are heavily reinforced with internal webbing orstitfeners to provide sufficient strength at the corners of thecompleted insulation system to safely withstand the accumulated thermaland mechanical stresses which tend to arise at such corners when exposedto cryogenic temperatures.

As a further important aspect of the invention, the lug panels have endedges which are ascendingly and descendingly stepped and are interlockedto establish extremely rigid joints, the configuration of whichsubstantially reduces the possibility of escaped cryogenic cargo seepingtherethrough.

For a more complete understanding of the invention and its attendantadvantages, reference should be made to the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic cross-sectional view of a cargo hold of a doublehulled tanker including the insulation system of the present invention;

FIG. 2 is a perspective view of a reinforced, molded three-dimensionalcorner wall panel embodying the principles of the invention;

FIG. 3 is a fragmentary, perspective view of a corner of an insultedtank showing the interrelationship of the wall panels and plug panels;and

FIG. 4 is a cross-sectional view of a plug panel showing the alternateend edge configurations thereof.

Referring to FIG. 1, the overall shape of the insulating barrier of theinvention is determined by and generally duplicates that of the innersteel walls 11 of a cargo space 12 of a double hulled vessel 13 ofconventional construction.

Specifically, the inner walls 11 are completely clad with thermalinsulation panels 14 to form a so-called secondary cargo barrier whichfunctions to insulate an inner tank 9 or integral primary cargo barrier(not shown), to provide an impermeable barrier for any leakage ofliquefied natural gas and thus protects the vessel structure from thepotentially deleterious effects of the supercooled cargo.

In accordance with the invention, the barrier 10 is established by aseries of discrete insulation panels 14, the majority of which arerectangular in shape and characterized as being generally flat. Thesegenerally flat panels are designated by reference number 15.

The corners of the cargo space 12 are clad by new and improved L-shapedpanels 16 and boxlike panels 17. In accordance with the inventiveprinciples, the panels 16, 17 include transverse internal membranes 18which provide sufificient strength and rigidity to the corner panels 16,17 to enable them to withstand the accumulated thermal stressconcentrations which tend to localize at the corners of the insulationbarrier 10 while it is in service. As shown, the edges of corner panels16, 17 are beveled so that they may cooperate with the walls 11 of thesupporting structure of triangular cross section to define a channel 19which may be monitored for gas leakage, the detection of which would, ofcourse, indicate a failure of the cargo barrier. The wall panels 15, 16,17 are fabricated of molded shells 20 of polyester resins reinforcedwith fiberglass, which shells encapsulate a polyurethane foam filling21, in accordance with the general teachings of copending applicationSer. No. 394,287 of Pratt et al., for Insulation System, filed Sept. 3,1964.

In accordance with the invention, the side edges of all of the wallpanels 15, 16, 17 are ascendingly stepped with the innermost or cold (interms of the relation of the installed barrier to the cargo) surfaces ofthe panels defining the top step 22, and the outermost or warm surfacesof the panels defining the bottom step 23, there being one intermediatestep 24, as shown.

The wall panels 1517 are appropriately afiixed to the walls by suitablemeans, for example, by using screws and adhesive as described in detailin the above-identified application, in a manner in which theirascendingly stepped edges are parallelly arrayed to define an open gridG. In accordance with the invention, the insulating cargo impermeablebarrier 10 is completed by filling the spaces between wall panels, i.e.,the open grid G, with straight plug panels 26 and L-shaped plug panels27 formed similarly to the wall panels 15-17 of molded fiberglassreinforced polyester shells which encapsulate polyurethane foam. Theplug panels 26, 27 may be secured to the wall panels 1517 by adhesivesand screws in a manner illustrated in the aforementioned applicationSer. No. 394,287. Thus, as shown in FIG. 3, the gaps between adjacentwall panels 15-17 are filled with appropriately shaped generally flatplug panels 26 and the gaps of the grid G located at the corners of thetank are filled by L-shaped plug panels 27. It should be understood thatthe illustrated corner intersection of three walls of the barrier 10embodies all of the shapes of wall panels and plug panels employed incladding the walls 11 of the cargo hold 12.

In accordance with the invention, the end edges 28 as well as the sideedges 29 of the plug panels are stepped. More specifically, three of thefour end edges of the plug panels meeting at every grid intersection areascendingly stepped and arranged to terminate in alignment with theedges of the wall panels forming the intersection, as shown at therighthand side of the drawing in FIG. 3. The remaining plug-panel whichmeets at the intersection and completes the joint has a descendinglystepped, extended edge 30 which engages in mating fashion all four ofthe wall panels at the intersection and the other three lug panels. Aswill be understood, the side edges 29 of all plug panels aredescendingly stepped while the end edges may be either ascendingly ordescendingly stepped (plug panels with both types of ends being shown inFIG. 4). However, at each grid intersection, only one of the end edgesof the four plug panels meeting at the grid intersection is descendinglystepped. Furthermore, the plug panel having the descendingly stepped endedge will be of sufficient length to extend across and to completelyfill in the space of the intersection.

Accordingly, it should be understood, at every grid intersection, theextended plug panel end edge (which is descendingly stepped) overlapsand mates wit-h the ascendingly stepped edges of the four wall panels,and the three plug panel end edges defining the intersection.Furthermore, all the four side edges of all of the plug panels overlapthe ascendingly stepped edges of the wall panels. Therefore, inaccordance with the invention, this overlapping, interlockingarrangement of plug and wall panels establishes a substantially rigidbarrier, the joints of which provide a tortuous and substantiallyimpenetrable path for escaped cryogenic cargo. Accordingly, the new andimproved barrier construction tends to minimize strike through ofliquefied natural gas that may have leaked through a primary barrier.

It should be understood that the specific structure herein illustratedand described is intended to be representative only, as certain changesmay be made therein with out departing from the clear teachings of thedisclosure. Accordingly, reference should be made to the followingappended claims in determining the full scope of the in vention.

What is claimed is:

1. A continuous insulating barrier construction comprising (a) a closedsupporting structure having inner surfaces of predetermined geometricconfiguration;

(b) a plurality of insulation wall panels secured to said inner surfacesof said supporting structure;

(c) said wall panels having ascendingly stepped side edges defining agridlike network of gaps therebetween;

(d) a plurality of insulation plug panels filling the gaps betweenopposed longitudinal sides of said wall panels;

(e) each intersection within the gridlike network being filled by anintegral extension of one of said plug pieces;

(f) said extension engaging the ends of three other plug piecesterminating at said grid intersection;

(g) the innermost layer of said extension being superimposed upon theintermediate layers of said three other plug pieces and the intermediatelayers of at least portions of the four wall panels defining said gridintersection.

2. A barrier construction in accordance with claim 1,

in which (a) the intersections of adjacent walls of said barrier beingformed -by molded L-shaped wall panels and plug panels;

(b) the corner intersections of three walls of said barrier being formedby molded boxlike wall panels having portions coplanar with each of theintersecting walls.

3. A barrier construction in accordance with claim 2,

in which (a) said boxlike and said L-shaped wall panels includesufficient reinforcement to withstand stresses developed therein.

4. A barrier construction in accordance with claim 1,

in which (a) all of the side edges of said plug panels are descendinglystepped;

(b) one of the four end edges of the plug panels meeting at eachintersection is descendingly stepped;

(c) the end edges of the other three plug panels meeting at saidintersection are ascendingly stepped.

References Cited UNITED STATES PATENTS 3,158,459 11/1964 Guilhem 220153,298,345 1/ 1967 Pratt.

3,339,780 9/1967 Forman et a1.

3,341,051 9/1967 Forman et al.

THERON E. CONDON, Primary Examiner.

J. R. GARRETT, Examiner.

1. A CONTINUOUS INSULATING BARRIER CONSTRUCTION COMPRISING (A) A CLOSEDSUPPORTING STRUCTURE HAVING INNER SURFACES OF PREDETERMINED GEOMETRICCONFIGURATION; (B) A PLURALITY OF INSULATION WALL PANELS SECURED TO SAIDINNER SURFACES OF SAID SUPPORTING STRUCTURE; (C) SAID WALL PANELS HAVINGASCENDINGLY STEPPED SIDE EDGES DEFINING A GRIDLIKE NETWORK OF GAPSTHEREBETWEEN; (D) A PLURALITY OF INSULATION PLUG PANELS FILLING THE GAPSBETWEEN OPPOSED LONGITUDINAL SIDES OF SAID WALL PANELS; (E) EACHINTERSECTION WITHIN THE GRIDLIKE NETWORK BEING FILLED BY AN INTEGRALEXTENSION OF ONE OF SAID PLUG PIECES; (F) SAID EXTENSION ENGAGING THEENDS OF THREE OTHER PLUG PIECES TERMINATING AT SAID GRID INTERSECTION;(G) THE INNERMOST LAYER OF SAID EXTENSION BEING SUPERIMPOSED UPON THEINTERMEDIATE LAYERS OF SAID THREE OTHER PLUG PIECES AND THE INTERMEDIATELAYERS OF AT LEAST PORTIONS OF THE FOUR WALL PANELS DEFINING SAID GRIDINTERSECTION.